Sorry you are having rough patch.
Your brain has that thing it calls elasticity, look up re wiring your brain concussion on google. I lost cognitive and awareness, but I think it was because I was under pain for over a year without expert treatment.
don't underestimate the negative power that your negative thoughts will produce on you. Try to be positive, it could be much worse...

You are young, so your brain is so fantastic, that you can actually do a full recovery. Might want to shift your attention from football, into something else.
I think the teachers are right for no mercy , reason is, they are giving you the opportunity to become even better than you were before .
I suggest to not blame the teachers, things happen anyway, so just try to do your thing to recover. everything else can wait, or you can try to do something else.
Extra virgin coconut oil and good quality fish/krill oil are awesome for your brain too.

I take Ginko biloba once in a while and i think it helps me too.

Good luck and stay strong!!!